This invention relates to methods for connecting semiconductor devices onto substrates and, in particular, to a method particularly useful for connecting devices requiring hermetic sealing.
In the fabrication of practical electronic circuits, semiconductor devices are connected to leads on a substrate such as an insulating ceramic. Such connections need to be made with minimal electrical impedance, minimal thermal impedance, and with hermetic sealing of the interconnect region. Resistive and inductive impedance limit speed. Thermal impedance limits power, and moisture limits operating life.
High performance devices such as avalanche and PIN photodiodes are typically sealed within metal or ceramic packages in a controllable gaseous ambient. In a typical arrangement, a planar avalanche photodiode (APD) is mounted within a ceramic package over an opening to provide back-illumination of the diode. The ceramic package is then sealed in an inert gas ambient by a metal lid. This process is quite expensive.
Accordingly there is a need for an improved method of mounting and interconnecting semiconductor devices.
In accordance with the invention, a semiconductor device having an electrical input/output contact surface is hermetically sealed and provided with connections via a submount such as a two-level ceramic substrate. The device is provided with a contact surface having a sealable peripheral contact and one or more interior contacts. The submount is provided with a sealable peripheral contact corresponding to the device peripheral contact and one or more feed-through contacts corresponding to the device interior contacts. The sealable peripheral contacts surround the interior contacts to provide heremetic sealing.